Much electronic apparatus requires cooling. In many cases this is effected by blowing air through an external enclosure that contains the electronic apparatus via vents in the external enclosure. Within the external enclosure, components that generate large amounts of heat may be mounted on heat sinks either individually or in groups.
In some situations, for example when the apparatus is to be used outside, the external enclosure must be environmentally sealed. One example of this is base station equipment for a mobile communications network, where an external enclosure containing a transmitter/receiver, a power amplifier, a processor and other units, is mounted outside e.g. on a pole.
The environmental seal prevents air from being blown through the external enclosure. Conventionally, the environmentally sealed external enclosure may be provided with extended surfaces to increase its surface area, thus allowing the whole external enclosure to be cooled by convection. In some instances it is difficult to cool the external enclosure sufficiently, particularly in the region of the components that generate relatively large amounts of heat.